Subdiv won't go to component mode
Hello. Using Maya 8.5 on Precision 690. 2 GB RAM. OS: XP-Pro
I am working on a project now for a few months. Yesterday one of the polys in the scene, when in subdiv all of a sudden won't allow me to go in to component mode. The RM hotbox over the subdiv is the same as if it were still a regular polygon,and also I can't actually select vertices, faces or edges. If I choose vertices, for example, the subdiv changes color from object mode green to component mode blue, but none of the vertices appear. The same happens if I try selecting faces or edges. If I convert the subdiv back in to a polygon, I can now switch to component mode and select the various components fine. Only in subdiv is there this problem.
Meanwhile, other subdivs in the scene still act normally, as this one did up until yesterday.
Why has this happened to this one subdiv and how can I fix it?
I have tried hunting the hypergraph for extraneous nodes which may be causing this but so far no luck.
Anyone know what to do?